net: sched: u32: Add test case for systematic hnode IDR leaks

Add a tdc test case to exercise the just-fixed systematic leak of
IDR entries in u32 hnode disposal. Given the IDR in question is
confined to the range [1..0x7FF], it is sufficient to create/delete
the same filter 2048 times to fill it up and get a nonzero exit
status from "tc filter add".

Signed-off-by: Alexandre Ferrieux <[e-mail]>
Acked-by: Jamal Hadi Salim <[e-mail]>
Reviewed-by: Victor Nogueira <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Paolo Abeni <[e-mail]>

tools/testing/selftests/tc-testing/tc-tests/filters/u32.json

···
         "teardown": [
             "$TC qdisc del dev $DEV1 parent root drr"
         ]
+    },
+    {
+        "id": "1234",
+        "name": "Exercise IDR leaks by creating/deleting a filter many (2048) times",
+        "category": [
+            "filter",
+            "u32"
+        ],
+        "plugins": {
+            "requires": "nsPlugin"
+        },
+        "setup": [
+            "$TC qdisc add dev $DEV1 parent root handle 10: drr",
+            "$TC filter add dev $DEV1 parent 10:0 protocol ip prio 2 u32 match ip src 0.0.0.2/32 action drop",
+            "$TC filter add dev $DEV1 parent 10:0 protocol ip prio 3 u32 match ip src 0.0.0.3/32 action drop"
+        ],
+        "cmdUnderTest": "bash -c 'for i in {1..2048} ;do echo filter delete dev $DEV1 pref 3;echo filter add dev $DEV1 parent 10:0 protocol ip prio 3 u32 match ip src 0.0.0.3/32 action drop;done | $TC -b -'",
+        "expExitCode": "0",
+        "verifyCmd": "$TC filter show dev $DEV1",
+        "matchPattern": "protocol ip pref 3 u32",
+        "matchCount": "3",
+        "teardown": [
+            "$TC qdisc del dev $DEV1 parent root drr"
+        ]
     }
 ]